how to change ospf interface cost dynamically

hi: I have two ospf interfaces between two routers. sometimes I want to use one of the interfaces to transfer data, and sometimes I want to use another. I think I can change configuration of interface cost and issue bird reload every time I need to switch interface. but I wonder if there is smarter way. any possibility I can change some interface parameters by linux system commands, so bird would change ospf cost dynamically? or can I tell bird to change interface cost dynamically? thanks a lot for suggestion!